ISC 2026 Biotechnology Improvement Examination Question Paper for Class 12

About this paper

This is ISC Class 12 Biotechnology Paper 1 (Theory) from CISCE's 2026 Improvement Examination, paper code 878A (printed as 1226-878A-IE). It carries 70 marks and runs for three hours, with fifteen minutes extra for reading. All 12 questions are compulsory. Section A is 14 marks of very short answers, including pBR322 selection, DNA profiling steps and two assertion–reason items. Section B has seven four-mark questions and Section C four seven-mark questions, with an internal choice in two questions of Section B and one of Section C. Later questions cover Sanger sequencing, a gene gun, protoplast fusion, and three ways of screening recombinants: a jellyfish fluorescent protein, lacZ, and ampicillin–tetracycline replica plating. This copy has the questions only.

Exam

ISC Class 12

Subject

Biotechnology

Year

2026

Paper code

878A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

12

Pages

12

Answers included

No, questions only

Paper pattern

• Section A

  14 marks

  Question 1: ten very short-answer subparts totalling 14 marks, including two assertion–reason items

• Section B

  28 marks

  Questions 2–8, four marks each; internal choice in two questions

• Section C

  28 marks

  Questions 9–12, seven marks each, including a gene-gun figure and a screening passage; internal choice in one question

Topics covered

• DNA replication
• Meselson–Stahl experiment
• pBR322 and antibiotic selection
• DNA profiling
• Genetic code
• Bt crops
• Tryptophan operon
• Bacteriophage lambda
• Recombinant insulin and bioremediation
• DNA sequencing and genomics
• Gene gun and somatic hybridisation
• Reporter genes and blue-white screening

Questions from this paper

1. Name the proteins that keep the two DNA strands from rejoining after helicase has separated them during replication.
2. A DNA molecule is allowed to replicate for three cycles by the Meselson–Stahl protocol. What percentage of heavy nitrogen is detected in the penultimate generation?
3. Some colonies transformed with pBR322 grow on ampicillin but not on tetracycline. What does this indicate?
4. A sample contains eight DNA fragments, which are amplified for six cycles. How many fragments are present at the end?
5. Bacteriophage lambda has a linear double-stranded genome of 48,502 bp with COS sites at both ends. What are COS sites, and how is a desired gene incorporated into this phage?
6. In a gene gun the DNA is coated on gold particles. Why does the transfer fail if brass is used instead of gold?